1. Field of the Invention
The present invention relates to a method for growing a nitride semiconductor, and more particularly, to a method for selectively growing a nitride semiconductor of a hexagonal pyramid, a nitride light emitting device manufactured using the same method and a manufacturing method of the same device.
2. Description of the Related Art
Recently, a semiconductor light emitting device has been vigorously studied as a new light source to replace a filament-based bulb and a fluorescent lamp. Especially, attention has been drawn on a study on a light emitting diode (LED) using a nitride compound semiconductor such as GaN. A nitride crystal is accompanied by many crystal defects due to absence of an adequate substrate for growth thereof.
In an effort to overcome this problem, a light emitting structure of a hexagonal pyramid is selectively grown to produce a high-quality nitride light emitting device.
FIG. 1 is a cross-sectional view illustrating an example of a light emitting device of a hexagonal pyramid.
As shown in FIG. 1, a low-temperature buffer layer 12 is formed on a sapphire substrate 11. A base layer 13 made of a first conductive nitride is formed on the substrate 11. A dielectric layer M, with a window W formed therein, is formed on the base layer 13 of the first conductive nitride. A first conductive nitride crystal 14 of a hexagonal pyramid is formed on the window 1 to have crystal planes inclined with respect to a top surface of the base layer. Then, an active layer 15 and a second conductive nitride layer 16 are sequentially grown to produce a light emitting structure of a hexagonal pyramid.
At least one of a transparent conductive film 17 and an electrode 19 is formed on the second conductive nitride layer 16 of the hexagonal pyramid. The dielectric layer is partially etched to expose the first conductive nitride base layer 13, thereby forming another electrode of a different polarity.
While the nitride single crystal of the hexagonal pyramid grown selectively as described above is being grown laterally, many defects are removed from a lower part or altered in their direction, thereby rarely affecting the active layer. Moreover, in the nitride single crystal, inclined side surfaces substantially increase a light emitting area and a crystal growth direction alleviates a piezo-electric field effect.
However, despite the aforesaid advantages, the conventional nitride light structure of the hexagonal pyramid experiences a difference in the growth rate between the base and the apex of the pyramidal structure due to stress caused by the inclined side surfaces. This accordingly brings about difference in thickness and In content between a quantum well layer and a barrier layer. That is, as shown in FIG. 1, a portion of the active layer in the vicinity of the base of the pyramidal structure has a thickness smaller than a portion of the active layer around the apex thereof, thereby hardly obtaining light of a desired wavelength. Furthermore, the conventional nitride light structure has degraded p-doping characteristics due to stress induced by the inclined side surfaces.